Add an overlay reproducing missing devlink for LED using GPIO

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

Linux 5.6

Linux 5.6-rc7

Linux 5.6-rc6

Linux 5.6-rc5

Linux 5.6-rc4

Linux 5.6-rc3

Linux 5.6-rc2

Linux 5.6-rc1

Linux 5.5